SUSY Hadronic/GMSB Meeting

SUSY Hadronic/GMSB Meeting 26-08-10
MR draft SUSY Hadronic/GMSB Meeting Christopher Rogan California Institute of Technology

Christopher Rogan - SUSY All Hadronic/GMSB Meeting 26-08-10
The Search for SUSY Here we re-introduce a new set of variables for a fully-inclusive SUSY search: See talks in: SUSY meeting , HWW meeting or backup slides or In general, an analysis using these variables, relative to a canonical SUSY search looking in a MET/MHT/HT tail for an excess: Yields higher signal efficiency w.r.t. the inclusive SUSY x-section More control over background distributions Distinctive signature: tail search becomes bump hunt arXiv: v1 [hep-ph] BKG Log(N) Log(N) BKG BKG SIG SIG SIG x x’ Christopher Rogan - SUSY All Hadronic/GMSB Meeting 2

Kinematic Variables for SUSY
 Two variables designed to be used together for discovery  and characterization of SUSY arXiv: v1 [hep-ph] Doesn’t involve MET Uses both transverse and longitudinal information Invariant under long. boosts Peaks for signal: Dimension-less variable used for S/B discrimination Not only suppresses backgrounds, but also shapes their distributions in the variable in a predictable and well-understood way - the Razor 3 Christopher Rogan - SUSY All Hadronic/GMSB Meeting 3

Selection/Sample Details
For everything shown in this talk: 7 TeV MC (see back-up slide for list of samples) 7 TeV Data (up to run right now ~318 nb-1) OR of HT200 and Jet110 triggers (for the moment) PF MET used (tcMET or corrected caloMET fine too) Require di-jets satisfying (parallel analyses): NO explicit lepton/photon reco or ID in constructing these variables If > 2 reco jets, form two hemispheres by minimizing invariant masses added in quadrature (see back-up slides) Corrected Calo jets Corrected PF jets Uncorrected Track jets Loose jet ID Loose jet ID Only high quality tracks w/ vertex consistent with reco PV considered for clustering Christopher Rogan - SUSY All Hadronic/GMSB Meeting

The Razor in practice PF jets LM1 MC QCD MC (ALPGEN) Cut on R gives many orders of magnitude suppression of QCD background More importantly, cut on R dictates the shape of the surviving background events (QCD and others) in the variable MR (see next slide) Christopher Rogan - SUSY All Hadronic/GMSB Meeting

DATA behaves as expected
The Razor and MR PF jets DATA behaves as expected Backgrounds fall ~exponentially after exceeding relevant scale (set by process scale+trigger/reco requirements) - slope set by R cut Christopher Rogan - SUSY All Hadronic/GMSB Meeting

MC Search Expectations
PF Jet Analysis Normalized to 10 pb-1 Here, LM1 + largest bkgs There are two exclusive classes of events - analogous variables to R and MR defined also in the “primed” case (see arXiv: v1 [hep-ph]) See back-up for all signal and bkg tables Assuming reasonable precision for bkg estimates (see following slides) we should be sensitive to LM1 with ~10 pb-1 in PF jet analysis Christopher Rogan - SUSY All Hadronic/GMSB Meeting

Calo Jet Analysis Normalized to 10 pb-1 Here, LM1 + largest bkgs See back-up for all signal and bkg tables Assuming reasonable precision for bkg estimates (see following slides) we should be sensitive to LM1 with ~10 pb-1 in Calo jet analysis Christopher Rogan - SUSY All Hadronic/GMSB Meeting

Track Jet Analysis Normalized to 10 pb-1 Here, LM1 + largest bkgs See back-up for all signal and bkg tables Assuming reasonable precision for bkg estimates (see following slides) we should be sensitive to LM1 with ~10 pb-1 in Track jet analysis Christopher Rogan - SUSY All Hadronic/GMSB Meeting

Towards Background Estimations
To zero-th order, we can use low MR region to predict high MR background yield Can even go further by defining mutually exclusive “boxes” defined using lepton ID/tracker isolation (independent of definition of MR and R) As of now, 9 exclusive boxes: For a given bkg type, exponential slope in MR the same in each box (physics object final state independent) Two  at least one ISO Two , no ISO One e, one  ISO One e, one  non-ISO One  ISO One  non-ISO Two e One e Other Christopher Rogan - SUSY All Hadronic/GMSB Meeting

Towards Backgrounds Estimations
Using a loose R-cuts we have a QCD dominated sample which we can use to measure the QCD slope, as a function of R-cut, in the low MR region Can do this in any box with QCD population in low MR Christopher Rogan - SUSY All Hadronic/GMSB Meeting

Using a loose R-cuts we have W+jets dominated samples (single lepton boxes) which we can use to measure the W slope, as a function of R-cut, in the medium MR region (range depending on R-cut) Can do this in several different boxes, with several different R-cuts MC predicts same exponential slope for W/Z/top+X - don’t need to assume this though Christopher Rogan - SUSY All Hadronic/GMSB Meeting

Using a loose R-cuts we have top dominated samples (opposite flavor lepton boxes) which we can use to measure the ttbar slope, as a function of R-cut, in the medium MR region (range depending on R-cut) Can do this in different boxes, with several different R-cuts Christopher Rogan - SUSY All Hadronic/GMSB Meeting

Sensitivity comparable for each jet type considered
Discovery Potential 3 Observation 5 Discovery Here, we look at estimated sensitivity for a PF Jets based search, doing a counting experiment and estimating systematic uncertainty assuming ratios of events in control regions to signal region (conservative estimate) Sensitivity comparable for each jet type considered 14 14 Christopher Rogan - SUSY All Hadronic/GMSB Meeting 14

Outlook SUSY search using variables MR and R appears to have good potential for SUSY discovery - Simple analysis defined in a fully inclusive way (with variables that are independent of certain topological considerations) Construction of variables allows us to control background shapes - can easily evolve analysis as a function of integrated luminosity Work on background estimation techniques underway - with mutually exlusive box definitions we will be able to over-constrain the relevant backgrounds Immediate TODO: Analysis note nearly complete Additional jet types and MET types also (JPT, uncorrected jets, calo MET, tcMET) to be added for parallel analyses/cross-checks Analyze full available data-set Sensitivity estimations to be updated with “final” analysis when converged Christopher Rogan - SUSY All Hadronic/GMSB Meeting

BACK-UP SLIDES Christopher Rogan - SUSY All Hadronic/GMSB Meeting

SUSY dijets Let’s consider a SUSY di-jet final state topology where two squarks are produced and each decay to a quark and an LSP x z For the moment we neglect any potential transverse boost to the entire di-squark system (from ISR for example) Christopher Rogan - SUSY All Hadronic/GMSB Meeting

We define the variable MR as ( j1 and j2 are quark jets from previous slide): It is like a 1D analogue of the invariant mass, along the z-axis It is invariant under longitudinal boosts See paper for more details on it’s derivation: arXiv: v1 [hep-ph] Christopher Rogan - SUSY All Hadronic/GMSB Meeting

Properties of Returning to the di-squark example, if (the squarks are produced exactly at threshold) then We find that, even if deviates from 1 (which it will in practice) that MR still peaks For QCD di-jets (assuming no mis-measurements, no pt to dijet system etc.) Conceptually, we expect to see a peaking signal over a steeply falling background Christopher Rogan - SUSY All Hadronic/GMSB Meeting

The Razor Unfortunately, the rate of QCD (even at high ) is prohibitively high such that we will not be able to observe this signal without some additional discriminating variable(s) Such a variable is the Razor, denoted and defined as:( ) behaves similarly to the stransverse mass or , such that if Then has a kinematic endpoint at Hence, similarly to or , we take the ratio of two variables with dimension mass (or energy if you prefer) and cut on a scale-less variable. Christopher Rogan - SUSY All Hadronic/GMSB Meeting

Properties of As defined, MR is very robust against jet mis-measurements, especially ‘catastrophic’ under-measurements of jets’ energy This is because it is, in a sense, a geometric average of the two jet’s momentum The large transverse momentum imbalance that can result from jet mis-measurements or jets falling outside of phase-space acceptance, or unclustered energy - which can result in potentially large missing ET - is largely protected against by the use of the Razor. MTR and MR measure the same scale, but are also largely uncorrelated Rather than demonstrating this analytically, we will see some of these properties illustrated in these slides Christopher Rogan - SUSY All Hadronic/GMSB Meeting

Generalizing to an inclusive environment
Up until this point, we restricted ourselves to a 2 jet final state. For a number of reasons we would like to generalize to a multi-jet (or even fully inclusive) final state final state radiation will occur, and is something we don’t really capture in our current MC samples For better or worse, if nature includes SUSY then we shouldn’t restrict ourselves to looking for right-handed squarks decaying directly to LSP’s To do this, we will take all the jets (or all the objects) in our final state and group them into two mega-jets, or hemispheres In the following examples, we do this my minimizing the invariant masses of the two hemispheres We have studied several other “hemisphere” algorithms, and find that these results are not sensitive to this choice (since all the algorithms get the assignments often wrong anyway) Christopher Rogan - SUSY All Hadronic/GMSB Meeting

Toy examples What were our two jets are now two hemispheres, and MR is defined as before with this substitution (hemisphere masses set to zero, like jets) To understand what should happen to MR in a more general class of scenarios, we consider 3 toy examples: (A) production of two different heavy particles with (B) production of two identical heavy particles, with one decaying through the lighter massive particle and then to jet+LSP (C) Both identical heavy particles decaying like this A B C Christopher Rogan - SUSY All Hadronic/GMSB Meeting

Pythia vs. ALPGEN QCD Modeling
Pythia QCD ALPGEN QCD DATA For multi-jet analyses - especially those which rely on the angular correlations between jets - Pythia is NOT reproducing the observed data, qualitatively OR quantitatively Christopher Rogan - SUSY All Hadronic/GMSB Meeting

Calo Jet Analysis Normalized to 10 pb-1 Christopher Rogan - SUSY All Hadronic/GMSB Meeting

Track Jet Analysis Normalized to 10 pb-1 Christopher Rogan - SUSY All Hadronic/GMSB Meeting

PF Jet Analysis Normalized to 10 pb-1 Christopher Rogan - SUSY All Hadronic/GMSB Meeting

MC samples NLO x-sections from used when available for backgrounds, otherwise LO x-sections returned from generator Samples those listed in: PYTHIA: QCD, LM signal points, di-bosons, QCD di-photons MADGRAPH: Single top (s-chan,t-chan, tW), ttbar, W(l)+jets, Z(ll)+jets, Z()+jets, +jets ALPGEN: QCD (beginning to look at other bkg) Christopher Rogan - SUSY All Hadronic/GMSB Meeting

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